To date, three types of on-board switching solutions are implemented in the satellites to switch data packets of small size at relatively low bit rates.
The solutions of a first type use the ATM (“Asynchronous Transfer Mode”) or MPEG2-TS (“Moving Pictures Experts Group—Transport Stream”) protocols which allow for an effective switching of the packets concerned because of their small size and their fixed size. On the other hand, this type of switching results in an extremely high number of data packets to be processed, incompatible with the processing power constraints imposed by the onboard processors embedded onboard the satellites, if these extremely high bit rates are considered. Furthermore, these packet formats or these frame structures involve an overhead of significant size commensurately reducing the useful bit rate available.
The solutions of a second type are based on the generic stream encapsulation (GSE) protocol as defined in the ETSI (“European Telecommunication Standard Institute”) technical standard with the reference ETSI TS 102 606 V1.1.1 (2007-10) and entitled “Digital Video Broadcasting (DVB); Generic Stream Encapsulation (GSE) Protocol”. These solutions of the second type make it possible to somewhat limit the number of packets to be processed, although this number still remains very high. Furthermore, the variable size of these packets requires issues of segmentation and of concatenation to be managed, which limits the gains in terms of reduction of the complexity of the onboard processing operations.
The solutions of a third type are based, for their part, on the internet protocol and are well suited to internet traffic, but they also involve a large number of packets of variable size to be processed in the case of a high bit rate link. Furthermore, working at the IP level entails implementing onboard reassembly, which results in a significant increase in the onboard buffer memories and the onboard computing power needed.
In the case of very high capacity space systems, that is to say those having a transmission capacity greater than 10 Gbps (gigabits per second), the solutions described above require a very high onboard complexity, which linearly increases with the number of data packets to be processed.
The technical problem is how to significantly reduce the onboard processing operations on the satellites for the switching and the routing of data packets at very high bit rate transiting via a network of regenerative satellites, provided with inter-satellite links ISL or via a regenerative geostationary satellite provided with an internal router.